Steroids from the Brazilian Zoanthids Palythoa caribaeorum and Palythoa variabilis

Two unreported ergostane-type sterols 24(R)-7α-hydroperoxy-ergost-5-en-3β-ol and 6β-carboxyl-24(R)-(8→6)-abeo-ergostan-3β,5β-diol, along with seven known ones were isolated from the hexane and alcohol extracts from the zoanthids Palythoa caribaeorum and Palythoa variabilis. The structures of the new compounds were determined using spectroscopic techniques, including 1D and 2D nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HRESIMS), and comparison with data previously published. 6β-Carboxyl-24(R)-(8→6)-abeo-ergostan-3β,5β-diol showed moderate cytotoxicity against colon cancer cells (HCT-116) as previously described for others abeo-sterol derivatives.